Railway track circuit apparatus



June 18, 1940. R. MILLS 2,204,810

RAILWAY TRACK CIRCUIT APPARATUS Filed April l2, 1939 Z 3 I 3a 4,

Compalledby werf ballzzdmffzb eaadlfz'aaf: C' lNvENToR Patented June 18,1940 UNITED STATES PATENT FicE RAILWAY TRACK CIRCUIT APPARATUS RobertMills, Kew Gardens, N. Y., assignor to The Union Switch & SignalCompany, Swissvale, Pa., a corporation of Pennsylvania Application April12, 1939, Serial No. 267,482

v11 Claims.

My invention relatesl to railway track circuit apparatus, and has for anobject the provision of novel and useful apparatus for improving thecuitapparatus embodlying my invention in which v polarized line circuits areemployed for signal control." Fig. 2 is a diagrammatic view alsoembodying my invention and showing a modied form of a portion of Fig. linvwhich a neutral line circuit is employed. Fig. 3 is a diagrammaticview similar to Fig. 2, also embodying myinvention and showing anormally deenergized auxiliary relay.l Fig. 4 is a diagrammatic viewshowing my invention applied to a portion of single track.

In each of the several views, like reference vcharacters' designatesimilar parts.

In track circuits employing the usual form of primary-secondary trackrelay combination,the secondary relay operates directly on the primaryor track relay by cutting out a certain number of turns from the relaywinding when the section is unoccupied and inserting an equivalentresistor to replace the turns which have been'rendered ineffective..This whole operation is usually performed at the relay end of the trackcircuit.y ,Under certain conditions, however, it is advantageous topermit the secondary relay to perform its improved shunting operation atthe battery or feed end of the track circuit, especially` if approachlighted signals are employed which make available an auxiliary (approachlighting) relay at the signal location. This auxiliary relay may then beused to perform the additional function of improving the shuntingsensitivity of thetrack circuit in a manner which will be clear from thedescription which follows. In the particular embodments which I haveshown, the improved shunting sensitivity is obtained by increasing thetotal resistance in series with the battery at the feed end of the trackcircuit. This method is particularly advantageous in connection withtrack circuits in which it is important to conserve the track` batteryoutput as much as possible.

Referring now to Fig. l, the reference characters I and la designate therails of a stretch of track in which traffic moves in fthedirectionindicated by the arrow. The rails are divided by insulated rail joints 5to form a series of blocks of which only the blocks 2 3 and 3-4 areshown complete in the drawing. Block 3 4 includes the two cut sections3--3a and 3ft-4. The track circuit for block 2 3 includes a trackbattery TB, current limiting resistors l and 6, the rails of thesection, and the track relay 2TR. Each of the remaining track circuitsincludes corresponding apparatus designated by similar referencecharacters except for identifying numerals corresponding to thelocation. Trame entering each block isA controlled 'by a suitable signalS which, as here illustrated, is of the color light type capablel ofdisplaying a green, yellow, or red indication as demanded by traiiicconditions in advance.

Each signal is governed by a line relay HDR, `here vshown as a polarizedrelay,^which is controlled by its associated track relay TR and the`line relay I-IDR at the signal next rin advance. Looking at line relay2HDR, the polarized, -line circuit for this relay is controlled by thetrack relay ZTR. over its front contact 8 and pole changing contacts Sand lil of the line relay :tI-IDR. next in advance. The line relays HDRare of the slow pick-up type and are so designed that their frontcontacts remain closed during a reversal of the polar contact structure.A relay which operates in this manner and is suitablevfor use herein isshown and described in Letters Patent of the United States No. 2,063,300granted December 8, 1936 toArthur E. Dodd, for Railway track circuitapparatus. controlled by a front contact H ofthe associated track relayto prevent release of its neutral arma-4 ture during a reversal of thepolar armature, but since the structure of this relay forms no part ofmy present invention no further description of this relay isnecessaryfor an` understanding of my invention. y It should be pointedout that-if an HDR relay of the retained neutral armature rtype is notavailable, proper signal control and selection may be obtained by an HDRrelay of the usual polarized type operating in conjunction with anadditional slow acting repeater relay which pole changes the linecircuit to the rear. This alternative combination of an HDR relay with aslow acting repeater represents well-known signaling practice and neednot be described in detail as it also forms no part of my presentinvention. f

At each signal location I have shown anyauxiliary relay ER which isconnected in series with the winding of the HDR relay next in the rear.Relay ER. may be the usual approach lighting re- This relay has aretaining Winding lay which causes illumination of its associated signalonly upon the approach of a train. When such relays are alreadyavailable in the system, no additional relays are required for carryingout the purposes and objects of my invention. In accordance with niyinvention, the approach lighting relay is caused to perform, in additionto its approach lighting function, the function of a secondary relay ofa primary-secondary track relay combination in that it operates toimprove the shunting sensitivity and decrease the power consumption ofits associated track circuit by introducing additional resistance inseries with the battery when the section becomes unoccupied. Thisoperation will be best understood by considering certain typical traicconditions.

With no train occupying the blocks shown, or the two blocks immediatelyin advance of signal 4S, all of the track relays, line relays, andapproach lighting relays are energized to the positions shown, wherebythe circuit for lamp G of each signal is prepared, but the signal isdark because of the open circuit at back Contact I2 of each relay ER.Under this condition, the short-circuit around resistor 'f in the trackbattery circuit is open at back contact I3 of each relay ER so that thetrack relay current is reduced, with a resulting increase in shuntingsensitivity and saving in track power input. At the cut section location3a, I have shown adjoining track feed apparatus for both of the trackcircuits 3 3a and 3a 4. This apparatus arrangement permits the auxiliaryrelay SAER to control not only the resistor l of its associated trackcircuit. but also to control over its back contact I4 the correspondingresistor of the adjoining track circuit.

When a train enters block 2 3, the track relay ZTR will release and inso doing will open the line circuit which supplies operating current torelays ZHDR and 3ER so that both of these relays will also release. Theclosing of back contact I5 of relay ZHDR will illuminate the the stoplamp R of signal 2S, and the closing of back contact I2 of relay 3ERwill illuminate the proceed lamp G of signal 3S over obvious circuits,each of which starts at one terminal B of a suitable source of current(not shown) and ends at the other terminal C of the same source. At thesame time, the closing of back Contact I3 of relay 3ER will shunt theresistor 'I in order that the track relay ZTR may pick up readily whenthe train vacates the section.

When. the train enters section 3 3a, the release of track relay 3TR willopen the line circuit which energizes all three of the relays 3HDR, SAERand 4ER so that all of these relays Will release. As a result, theproceed lamp G of signal 4S will become lighted over back contact I2 ofrelay dER, and signal 3S will change its indication from proceed to stopdue to the closing of back contact I5 of relay SHDR. The release ofrelay SHDR serves to pole-change the line circuit to the rear so thatwhen relay ETR subsequently picks up and closes the line circuit, relayZHDR will be energized in the reverse direction from that shown, inorder that the caution lamp Y of signal 2S may become lighted upon theapproach of a following train. The release of relay SAER will close ashunt for resistor 1 at back Contact I3, thus preparing the trackcircuit for pick-up of relay STR when the train vacates the section. Atthe same time, resistor I of the forward cut section is short-circuitedover back contact I4 of relay AER. This last operation does not entailany undesired consequences because the line circuit is already open atiront contact 8 of relay STR, so that relay SATR will have ampleopportunity to release before the train finally clears the rear cutsection 3 3a. When the train passes location 4, relay dTR will release,opening the circuit for relay HDR and causing signal 4S to display itsstop indication.

As soon as the train completely clears section 2 3, relay ZTR will pickup, thus completing a reverse energizing circuit [or relay ZHDRwhereupon polar contact I6 of this relay will swing to the right so thatsignal 2S will be conditioned to display a caution indication at lamp Yfor a following train. Completion oi the line circuit will pick up relay3ER which will open back contact I3 to restore high shunting sensitivityand low power input to the track circuit of block 2 3. The opening ofback contact I2 of relay 3ER also insures that once relay 3HDR picks up,signal 3S will become extinguished, provided a following train has notentered section 2 3.

When the train vacates section 3 3a, relay STR will pick up but nothingfurther will happen until the train completely clears section 3(1 4 sothat relay SATR will pick up. When this occurs, the line circuit forblock 3 4 will be energized with current of reverse polarity and all ofthe relays SHDR, SAER and 4ER will become energized. The current inrelay BHDR will be of reverse polarity so that signal 3S will beconditioned for displaying a caution indication. The pick-up of relaySAER will restore the sensitivity of both track circuits 3 3a and SrL-4. Also, the pick-up of relay AER will prepare the deenergization ofsignal 4S once the train Clears the block in advance of location 4,provided no following train is approaching.

When the train finally clears the block in advance of location 4, relayll-IDR will become energized and all of the apparatus will then berestored to the condition in which it is illustrated in the drawing.

It will be apparent from the foregoing description of Fig. 1 that I haveprovided apparatus at the track feed end of the block operating inconjunction with the track relay for controlling the sensitivity of thetrack circuit and that this apparatus may be a part oi the approachlighting or other approach control apparatus associated with the trackcircuit.

Referring to Fig. 2, this gure shows a single track circuitcorresponding, for example, to block 2 3 of Fig. l but employing anon-polarized or neutral line circuit suitable for two-positionsignaling. Relay HDR may. in this modification, be an ordinary slowpick-up neutral relay controlled over the line circuit in series withrelay ER, as in Fig. l.. When the section is occupied, relays TR, HDRand ER will all be released and resistor 'I will be short-circuited overback contact I3 of relay ER. Contact 25 may control suitable signalingapparatus, as in Fig. 1. When the section. is vacated, these relays willbe picked up and the opening of back contact I3 of relay ER will restorethe high shunting sensitivity and low power input to the track circuit.Additional control by advance traic for the line circuit of Fig. 2 maybe provided. if desired, but is not essential for the practice of myinvention. One form of such additional control is shown, for example, inblock 3 4 of Fig. l.

Referring to Fig. 3, this gure differs from Figs. l and 2 chiey in thatI have provided a esv normally' deenergized relay lER.. This arrange'-rnent' is 'somewhat safer in that a broken 'Wire'or otherfailureoftherelay ER to pick -up results in a decrease rather than an increase ofenergy relay is energized locally, in the' usual manner. An adjustableresistor l'l is included in the line circuit in ordei` to adjust thecurrent in this circuit with respect to the pick-up and release valuesof relay ER so as to obtain sensitive operation.' When a train occupiesthe section, relay ElR will be picked up over a circuit which includesone terminal of battery TB, the upper rail, wires 20' and 2|, backcontact I9 of relay TR, Athe line wire 2'2, resistor l'l, and winding ofrelay ER,

to the `other terminal of battery TB. Since relay ER is now picked up,its front contact lI8 is closed,'thus shunting out resistor 'l under theoccupied condition as in the two previous figures. Contact Zii'may'control signaling apparatus, as before. When the train leaves thesection, relay TR will pick up, openingA back contact I9 to deenergizethe line circuit so as to release ER and restore the unshunted conditionof resistor .'l.

' Referring to Fig. 4, this figure shows my invention applied to aportion of single track in which trafiic may move in either direction.In this figure, the winding of relayv ER is included in the line circuitfor the HDR relay as in Fig. l, and the voperation of the apparatus as awhole will 'be clear from the description presented in connection withFig. l. It will be noted that the resistor 'l for each track circuit'isshunted by l back contacts i3 and Ill in series of the two ER relays,both of these relays beingv released due to the opening of frontcontacts 23 and 2d of the TR relay when a train enters the section fromeither end. 'The complete control of the eastbound and westbound linecircuits is not shown as this control is well known and forms no part ofmy invention. It will be apparent that I have provided'in Fig. la simpleand compact arrangement'of apparatus forv improving the y shuntingsensitivity and decreasing the power input of trackcircuits for singletrack, two-direction signaling. y l

Although I `have herein shown and ldescribed only 'a' few forms ofrailway track circuit apparatus embodying my invention, it is understoodthat various changes and modifications may be made therein within thescope of the appended claims without departing from the spirit and scopeof my invention.

Having thus described my invention, what I claim is:

1. In combination with a section of railway track, a track relayreceiving current from the rails at one end of said section, a source oftrack circuit current at the other end of said section, a currentlimiting device at said other end of the section for limiting thecurrent supplied to the rails from said source, an auxiliary relay atsaid other end of the section, a line circuit for energizing saidauxiliary relay including a contact of said track relay, means includinga contact of said auxiliary relay effective when said section isunoccupied for increasing the effective value of said current limitingdevice to thereby increase the shunting sensitivity of said tracksection and decrease the power input thereto,

2. In combination with a section of railway track, a track relayreceiving current from thev rails at one end of said section, a sourceof trackl circuit current at the other end of said section, a currentlimiting'devi'ce at said other end of the section for limitingy thecurrent supplied tothe rails from said source, an auxiliary relay/atsaid Aother end of the section, a line circuit governed by said trackrelay for controlling the operation of said auxiliary relay, meanscontrolled by said auxiliary relay for at times increasing the effec-vtiveness 'of said current limiting device to thereby increase theshunting sensitivity of said track section and decrease the power inputthereto, and approach control means governed by said auxiliary relay,whereby'said auxiliary relay combines the functions of an approachvrelay and a secondary relay.

A'3.'In combination with a section of railway track, a track relayreceiving current from` the rails at one end of said section, a sourceof track circuit current at the other end of said section, a currentlimiting device at said other end of the section for limiting thevcurrent supplied to the rails from said source, an auxiliary relay atsaid other end of the section, a line circuit for energizing saidauxiliary relay including affront contact of said track relay, meansincluding av back contact of said auxiliary relay .for decreasing theeffectiveness of said current limiting defvice when said section isoccupied, and ap proach control means governed by a second back contactof said auxiliary relay, wherey said auxiliary relay combines theIfunctions of an approach relay and alsecondary relay.

.4. In combination with a section ofrailway track, av track relayreceiving current from the' rails at one end of said section., asourceof track circuit current at thefother end of said section, a.`current limiting device at said other end of the section for limitingthe current supplied to the rails from said source, an auxiliary relaysat said other end of the section, a line circuit for v'energizing saidauxiliary relay including a back contact of said track relay, meansincluding a front contact of said auxiliary relayfor decreasing theeffectiveness of said current limiting device when said section isoccupied, and approach control means governed by said auxiliary relay,whereby said auxiliary relay combines the functions of an approach relayand a secondary relay.

5. In combination with a section of railway track, a track relayreceiving current from the rails at one end of said section, a source oftrack circuit current at the other end of said section, a currentlimiting device at said other end of the section for limiting thecurrent supplied to the rails from said source, an auxiliary relay atsaid other end. of the section, a circuit controlled by said track relayfor energizing said auxiliary relay from said source over a line wireand a rail of said section, and means controlled by said auxiliary relayfor decreasing the effectiveness of said current limiting device whensaid section is occupied.

6. In combination, two adjoining sections of railway track having theirfeed ends at the junction of said two sections, a track relay for eachsection, a source of current for each section 1ocated at the respectivefeed end thereof, a current limiting device for each of said sources forlimiting the current supplied thereby to the respective track section,an auxiliary relay associated with said sources at the track feedlocation for said two sections, a line circuit for energizing saidauxiliary relay including a contact of the track relay for each of saidtwo sections, and means governed by said auxiliary relay for controllingthe effective value of each of said current limiting devices, wherebysaid one auxiliary relay performs the functions of a secondary relay forboth said track relays.

7. In combination, two adjoining sections of railway track having theirfeed ends at the junction of said two sections, a track relay for eachsection, a source of current for each section located at the respectivefeed end thereof, a current limiting device for each of said sources forlimiting the current supplied thereby to the respective track section,an auxiliary relay associated with said sources at the track feedlocation for said two sections, a line circuit for energizing saidauxiliary relay including a front contact of the track relay for each ofsaid two sections, and means including back contacts of said auxiliaryrelay for controlling the effective value of each of said currentlimiting devices, whereby said one auxiliary relay performs thefunctions of a secondary relay for both said track relays.

8. In combination with a stretch of single track railway in whichtraflic may move in either direction over the stretch, two track circuitsections for said stretch having their feed ends adjoining, a trackrelay for each section, a source of current for each section located atthe respective feed end thereof, a current limiting device for each ofsaid sources for limiting the current supplied thereby to the respectivetrack section, an auxiliary relay for each of said sources located atthe feed end of its respective track circuit, a line circuit for eachauxiliary relay controlled by both said track relays, and means governedjointly by said auxiliary relays for controlling the efective value ofeach of said current limiting devices.

9. In combination with a section of railway track, a track relayreceiving current from the rails at one end of said section, a source oftrack circuit current at the other end of said section, a currentlimiting device at said other end of the section for limiting thecurrent supplied to the rails from said source, an approach controlrelay at said other end of the section, a

line circuit for said approach control relay governed by said trackrelay, signaling apparatus governed by said approach control relay, andmeans also governed by said approach control relay for decreasing theeffectiveness of said current limiting device when said section isoccupied, whereby said approach control relay combines the functions ofan approach relay and a secondary relay.

10. In combination with a section of railway track, a track relayreceiving current from the rails at one end of said section, a source oftrack circuit current at the other end of said section, a currentlimiting device at said other end of the section for limiting thecurrent supplied to the rails from said source, a line relay at said oneend of the section, an approach control relay at said other end of thesection, a line circuit controlled by said track relay for energizingboth said line relay and said approach control relay, a signal for saidsection controlled by said line relay, signaling apparatus for thesection next in advance of said section controlled by said approachcontrol relay, and means also controlled by said approach control relayfor decreasing the effectiveness of said current limiting device whensaid section is occupied, whereby said approach control relay combinesthe functions of an approach relay and a secondary relay.

11. In combination with a section of railway track, a track relayreceiving current from the rails at one end of said section, a source oftrack circuit current at the other end of said section. a currentlimiting device at said other end of the section for limiting thecurrent supplied to the rails from said source, a signal control linerelay at said one end of the section, an approach control relay at saidother end of the section, a line circuit controlled by said track relayfor energizing both said line relay and said approach control relay inseries, signaling apparatus controlled by said approach control relay,and means also controlled by said approach control rela-y for decreasingthe effectiveness of said current limiting device when said section isoccupied, whereby said approach control relay combines the functions ofan approach relay and a secondary relay.

ROBERT MILLS.

